A bit late getting in on this one, but I had trouble getting my 240 to pass smog here in CA, the major reason being the cat was bad. The garage I usually use told me an easy way to check for proper function is to use an infrared thermometer to take temp readings of the exhaust pipe just before entering and just after leaving the cat. Because of the chemical reaction taking place in a properly working converter, the downstream temp should be significantly higher than the upstream temp. When I checked mine it was almost identical on both sides of the cat. This is a "quick and dirty" test, so it isn't 100% accurate in all scenarios, but if your cat is completely shot this will show it.